The present invention relates to the field of carpet manufacture, and more particularly relates to methods of treating carpet or carpet yarn to enhance its repellency and, preferably, to enhance its stain resistance also.
In the last two decades, there has been considerable interest in developing treatments for carpet fibers, particularly nylon carpet fibers, to enhance repellency and stain resistance. For example, it is now a common practice to topically apply a compound from the class known as fluorochemicals. The object of applying such fluorochemicals is to reduce the tendency of soil, oil and/or water to adhere to the carpet fibers. In addition to soil, the fluorochemicals can also reduce the tendency of oil and/or water to adhere to the carpet fibers. It is also a common practice to apply a stain resist compound to nylon carpet to make the nylon carpet fibers resistant to staining, particularly by anionic or "acid" dyes. The mechanism for stain resist compounds is believed to involve blocking of the dye sites on the nylon polymer.
The fluorochemicals include a fluorinated component, typically a perfluoroalkyl chain, and a nonfluorinated backbone. The nonfluorinated backbone can take a variety of configurations. The important feature of the backbone is that it is capable of forming durable film on the surface of the carpet fiber.
As to the mechanism of soil repellency, it is believed that the attraction between nonpolar soil and the fiber surface is governed by London dispersion forces. Applying fluorochemicals to the surface is thus believed to be effective because the polarizability of perfluoroalkyl chains is lower than that of the hydrocarbons, amines, or carbonyls otherwise found on the surface of a nylon carpet fiber.
Generally, fluorochemicals are topically applied to carpet. One method is to form an aqueous dispersion of the fluorochemical and then spray that dispersion on the top face of the carpet. Another method is to make an aqueous based foam containing the fluorochemical and then apply the foam to the top face of the carpet. Heat is usually applied to drive off excess water and to fix the fluorochemical to the carpet fibers.
Typically, stain resist compounds are applied to carpet from a bath after the dyeing step, but before drying. At least one system is commercially available wherein a fluorochemical and stain resist compound are topically applied in a foam. In particular, the FX-1367F fluorochemical composition and the FX-668F stain resist composition, both from 3M Specialty Chemicals Division, are recommended to be topically co-applied in a foam. The pH of the combined foam is about 4.